The use of phenolic polymers in photoresist compositions which are used in the fabrication of semiconductor devices is well known. Improvements in photoresists have created a need for resist components that have sufficient radiation or lithographic sensitivity to be of use in the fabrication of very large scale integration (VLSI) devices and ultra large scale integration (ULSI) devices. To meet these demands, chemically amplified photoresist compositions have been developed which generally comprise a polymer having acid sensitive functionalities and a compound which generates a strong acid upon radiation by UV light and/or electron beam (e beam) or x-ray radiation, referred to generally hereinafter as a "photoacid". The functionalized polymer reacts with the photoacid formed to fragment or release a portion of the functional group and regenerated acid to continue the photolysis or radiolysis reaction. Because a series of functional group changes can result from a single photon (or electron) absorbed, this process is referred to as "chemical amplification."
U.S. Pat. No. 4,491,628 to Ito et al. is directed to resist compositions or formulations comprising a polymer having recurrent acid labile groups (such as t-butyl esters and t-butyl carbonates) pendant to the polymer chain and a photoacid such that the acid labile groups undergo cleavage from the polymer upon the radiation of the composition and release of the photoacid. The photoacid is generated by an onium salt. These compositions were found to exhibit particularly desirable properties for photolithography in that they are positive or negative working based solely on the choice of developer solvents.
U.S. Pat. No. 4,552,833 to Ito et al. is directed to processes for generating negative images in a polymer film having masked reactive functionalities that is treated with an organometallic reagent after exposure and is dry developed with a reactive plasma after such treatment.
U.S. Pat. No. 4,613,398 to Chiong et al. is directed to processes for removing acid labile groups from polymer materials and treatment with organometallic agents so that the films may be dry developed.
U.S. Pat. No. 4,931,379 to Brunsvold et al. is directed to thermally stable resist compositions having secondary alkyl carbonates pendant to an aromatic group of a repeating polymer composition.
U.S. patent application Ser. No. 07/264,407, filed Oct. 28, 1989, to Merritt et al., Attorney Docket No. FI9-88-037, discloses certain partially t-butyloxycarbonyloxy substituted poly(p-hydroxystyrenes) and methods for their manufacture. These methods include acidolysis and thermolysis of poly(p-t-butyloxycarbonyloxystyrenes) and amine catalyzed carbonation of poly(p-hydroxystyrene) with di-tert-butyl dicarbonate.
Houlihan et al., Can. J. Chem., 63, 153 (1985), describes various mechanisms of phase transfer catalysis in the tert-butyloxycarbonylation of alcohols, phenols, enols, and thiols with di-tert-butyl dicarbonate. The tert-butyloxy-carbonylation of phenolic polymers such as poly-(p-hydroxystyrene) and novolaks was said to proceed rapidly and quantitatively with di-tert-butyl dicarbonate in THF, ethyl acetate, or dichloromethane, in the presence of a catalytic amount of crown ethers such as 18-crown-6 and an equivalent amount of powdered anhydrous potassium carbonate.
It is an object of the present invention to provide an improved method to manufacture carbonated hydroxyaromatic compounds which provide a uniform product and near quantitative yields. Carbonated hydroxyaromatic (particularly t-butyloxycarbonyloxy substituted) polymers and monomers are especially useful in resists for use in photolithography.